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From Sergey Shelukhin <ser...@hortonworks.com>
Subject Re: Problem In Understanding Compaction Process
Date Wed, 20 Feb 2013 22:07:50 GMT
There should be no duplicate records despite the file not being deleted -
between the records with exact same key/version/etc., the newer file would
be chosen by logical sequence. If that happens to be the same some choice
(by time, or name), still one file will be chosen.
Eventually, the file will be compacted again and disappear. Granted, by
making the move atomic (via some meta/manifest file) we could avoid some
overhead in this case at the cost of some added complexity, but it should
be rather rare.

On Tue, Feb 19, 2013 at 7:10 PM, Anty <anty.rao@gmail.com> wrote:

> Hi: Guys
>
>       I have some problem in understanding the compaction process, Can
> someone shed some light on me, much appreciate. Here is the problem:
>
>       Region Server after successfully generate the final compacted file,
> it going through two steps:
>        1. move the above compacted file into region's directory
>        2. delete replaced files.
>
>        the above two steps are not atomic, if Region Server crash after
> step1, and  before step2, then there are duplication records!  Is this
> problem handled  in reading process , or there is another mechanism to fix
> this?
>
> --
> Best Regards
> Anty Rao
>

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